1. Field of the Invention
The present invention relates to a write control for a recordable memory device.
2. Description of the Related Art
Size reduction of video recorders has made it necessary to record image data in a nonvolatile recording medium such as a memory card in real time. Recently, high quality of a video image has been realized. And so a stable write performance at a bit rate of about 4 MB/s for the video recorders has been required, simultaneously.
However, if memory data is managed using a file allocation table (FAT) file system, fragmentation of data occurs while a write or erase operation is repeated. As frequent occurrence of this fragmentation is a factor of remarkably reducing memory performance, it is difficult to perform the real-time recording.
In case of a NAND flash memory, write to a NAND block having fragmentation needs, in addition to real-time recording, that data already recorded in the NAND block must be newly recorded in another NAND block. Accordingly, overhead of write time occurs and the memory performance is reduced.
According to conventional real-time recording, if an error occurs, data transfer between a host apparatus and a memory card is temporarily stopped, and thereafter, retry must be done. Thus, write efficiency is reduced (e.g., see Jpn. Pat. Appln. KOKAI Publication No. 2004-326165).
During the retry, as real-time recording is not carried out, there is the possibility that data is lost.
Specifically, read/write of a memory card is controlled based on a command system of a random access memory. If an error occurs during real-time recording, the memory card gives an error notification to the host apparatus. When receiving the error notification, the host apparatus stops data transfer and then executes retry. Thus, image data obtained during the retry is not recorded in real time.
Considering the foregoing circumstances, it is desired to develop a technique capable of performing real-time recording at a stable write performance.